1. Field of the Invention
The present invention generally relates to a vehicle control device which performs braking control of a vehicle. More particularly, the present invention relates to a vehicle control device which enables the vehicle to pass through an intersection smoothly and safety with necessary minimum deceleration.
2. Description of the Related Art
Conventionally, the traffic control for making smooth the vehicle traffic is carried out by urging the observance of traffic control regulations. For example, the contents of the traffic control regulations are transferred from the infrastructure side to the drivers of respective vehicles by using the traffic signals installed at the crossings, the traffic-control signs installed along the roads, the stop lines drawn on the roads, etc.
In order to make the traffic control effective, it is necessary that the drivers of the respective vehicles keep in mind and understand the general traffic regulations, such as the meanings of the traffic control signs, and operate the respective vehicles to follow the traffic control regulations.
The cases in which the traffic control was carried out but traffic accidents have occurred are roughly categorized into: 1) the case in which the drivers did not follow or could not have followed the traffic control restrictions received from the infrastructure side; and 2) the case in which the infrastructure for the traffic control (traffic signals, etc.) was not ready and the contents of traffic control restrictions are indefinite for the drivers.
Conventionally, there has been proposed some techniques as the countermeasures for the above case 1). One of the techniques is to warn the driver of the vehicle concerned of existence of another vehicle with an excessive speed or crossing possibility, based on the information acquired using the vehicle-to-vehicle communication or the road-to-vehicle communication. Another technique is to support the operation of the driver of the vehicle concerned by performing automatic deceleration control of the vehicle in a special state. For example, see Japanese Laid-Open Patent Application No. 2002-140799.
However, according to the conventional technique disclosed in Japanese Laid-Open Patent Application No. 2002-140799, deceleration control is given to both the intersection passing vehicles, unless certain rules, standards, or agreements about intersection entry are set up in advance between the vehicles which are determined as having mutually crossing possibility. For this reason, the vehicles running through the intersection may not become smooth.
Moreover, there has been proposed some techniques as the countermeasures for the above case 2). According to the traffic control depending on the infrastructure, it is very difficult and unrealistic that all the intersections of all scales, such as large-scale intersections or small-scale intersections of residential street, are provided with the traffic signals and the stop lines. Inevitably, the intersection in which the traffic control is not practically carried out as in the case of the above item 2) may exist.
At such intersection where the traffic control is not practically carried out, the priority of intersection access will be indefinite to the drivers, and the actual traffic control will be entrusted to the discretion or mutual concession of the drivers who operate the vehicles accessing the intersection, which are uncertain factors. In fact, many of traffic accidents took place accidentally upon meeting suddenly in narrow street intersections without the traffic signal and stop line.
Another problem of the above-mentioned traffic control depending on the infrastructure is that the contents of the traffic control are fixed and cannot be dynamically adapted for changes of the traffic quantity.
In a certain limited area, the traffic signs indicating the contents of traffic control are changed or the lighting time of each of the colors of the traffic signals is changed on a week day or time zone basis. However, such techniques of the traffic control are carried out only in the limited areas only, and it is difficult for such techniques to change dynamically the contents of the traffic control on real time.
As mentioned above, in the case of the traffic control depending on the infrastructure, the prerequisite is that the drivers of the respective vehicles observe the traffic control directions indicated by the traffic signals, signs, etc. If the contents of the traffic control are fixed, the drivers of the respective vehicles must observe even when no crossing vehicles exist. For example, when no crossing vehicle exists but the stop line exists or the traffic signal is in red, the vehicle concerned must be stopped on the stop line or slowed down. This worsens the flow of traffic.
Thus, the traffic control depending on the infrastructure conventionally used as a matter of course has the following two problems: a) it is practically impossible to control all the intersections; and b) the control to stop or slow down the vehicles is performed unnecessarily even at the time of a small amount of traffic, and the unnecessary stop and unnecessary slowdown will worsen the flow of traffic.
In order to slow down or stop either of the crossing vehicles with the positional relationship having crossing possibility on a two-dimensional plane without using the traffic signals, signs, stop lines, etc. and allow the vehicles to pass through the intersection area smoothly, it is desirable to reconstruct the intersection having the crossing roads into a two-level intersection.
However, it is actually impossible to reconstruct all the existing intersections into two-level intersections.